What is a Prototype?

A Prototype is done in order to explore some aspect of a new opportunity without having to fully commit to it yet. Prototype has a number of potential meanings including:

the original or model on which something is based or formed.

someone or something that serves to illustrate the typical qualities of a class; model; exemplar:

something analogous to another thing of a later period:

Biology. an archetype; a primitive form regarded as the basis of a group.

So a Prototype is either an early model or a smaller scale development to test a new idea.

Why Prototype?

So for engineering, we Prototype to reduce risk, and we learn from Prototypes to improve the likelihood of project success by being better informed for the next round of design. So a Prototype is a core Product Development ProcessRisk Management strategy.

Product Development Process

A Prototype can also reduce other risks such as financial risk or market risk and isn’t always done for technical risk reasons.

Financial risk can be managed by breaking a project up into a series of stages and only committing funds to a stage when its predecessor has been successfully completed. A Prototype is often done ahead of a major block of Product Development to test whether the technical approach is likely to succeed and provide early warning of unexpected problems or interactions.

Market risk can be managed by trialing a new product idea with a smaller group of candidate customers to gauge their acceptance of the product. This has to be well managed however as history has shown that this approach, especially in the case of focus groups, can often just elicit the outcome the company hoped for and not a real example of how the market will react. Just look at all the failed Coca Cola new flavour launches.

And of course, technical risk can be managed by making Prototypes that implement the highest risk features as early as possible. We covered this in Improving Product Development.

And then having designed a product it is normal to build a Prototype to ensure the final solution works as expected. This manages the risk that production tooling might need rework or even redesign.

How to Prototype?

This depends on the problem you want to solve. For this section we will focus on technical risks. A Prototype is very useful to allow you to measure some essential elements of the final product without committing to a final solution. So you can explore:

modelling a problem and simulations

noise and interference

power consumption

performance versus cost (compare several different prototypes)

responsiveness

system resources required

hardware versus software solutions

temperature rise

materials properties

shape and usability / ergonomics

fit (especially PCBs in mechanical housings)

…

And the list can go on. The key is to determine where the risk is and manage that. In Project Management Pre-preparation we looked at using a Prototype to reduce both technical and financial risk at the same time. In this case, other developers hadn’t been able to produce a working product so the client had a clear risk to manage. And our approach was to make a jig that allowed us to explore the sensing that was needed and get real data to then analyse and develop a solution. The same jig allowed the solution to then be tested before we designed the Electronics PCBs and Embedded Software needed for the final product. And the client was able to authorise each next level of expenditure with confidence based on us having delivered against the requirements for the previous stage.

Simulation

And of course, 3D Printing for Electronics has enormously expanded the possibilities for mechanical prototypes by allowing anyone to quickly build and test the fit of objects together. It is also a viable option for low volume manufacturing.

Electronex

Electronex is the Australian Electronics Manufacturing industry annual expo. This year it is at the Melbourne Park Function Centre from Wednesday 6 to Thursday 7 September 2017. You can see all the details at Electronex.

Electronex 2017

SMCBA

In parallel the SMCBA (Surface Mount & Circuit Board Association) is running their annual conference. This year the primary sessions are:

The program has two internationally renowned presenters for SMT ManufacturingVern Solberg and Phil Zarrow presenting on the topics.

Vern Solberg

Phil Zarrow

And I’m presenting 2 of the open sessions which include a look at the role PCB Design takes in the overall Product Development and the 5 areas of cost you must manage if you want to minimise the total cost of a product.

PCB Design Tradeoffs

This topic looks at the Product Development process and how PCB design fits into that. This is to do with the trade offs between product features, what you do in HW, what you do in SW and how to select the technology you want to put on the PCB based on the combination of CEM or in house capability, component lead time, test requirements and product cost.

Total cost of product ownership

The total cost of ownership of a product is a concept that looks at all the investment required to bring a product to market and manage it throughout its life cycle. It isn’t just a case of minimising R&D spend or getting the Bill of Materials to a minimum. That will usually lead to a higher cost product.

What will be presented is a model looking at the 5 major costs areas involved in the development of a product throughout its life cycle and how taking all 5 into account can enable you to get the best return on the important investment made in bringing new products to market.

It will also examine a case study where a product development delivered a next generation product to market that allowed the manufacturer to lower their price, triple their profit margin and increase their market share, all at the same time.

Successful Endeavours Exhibiting

And we are also pleased to announce that we are exhibiting this year for the first time. So if you are coming then we are at stand C1 next to Duet Electronics.

Rapid prototyping, also referred to as 3D printing or additive manufacturing is the process of building objects or devices by building up layer by layer [1]. It has been identified as a potentially disruptive technology in the manufacturing industry in the coming years and is particularly well suited to provide benefits to technologies that operate on smaller scales of production [2]. New manufacturing paradigms, such as direct manufacturing (directly printing the sold goods) and home manufacturing (providing the capability for consumers to produce parts themselves) are set to change the way that small manufacturing businesses operate and significantly increase the level of competition in the industry [3].

This post will discuss the manufacturing technique of printing – a technology whose origins date back more than five centuries [4] and in this time a number of different printing methods have been developed. Successive layers are generally printed onto a substrate either by direct contact; via an impression cylinder (such as in flexographic, graviture or offset printing), deposited via a stencil (screen printing); or directly deposited onto the substrate (for example, inkjet printing, aerosol-jet printing or organic vapor-jet printing). Of these technologies, inkjet printing is particularly well suited to rapid prototyping and low volume manufacturing due to its high customisability, relatively high resolution and relatively low set-up cost [1].

Inkjet printed electronics differs to conventional inkjet printing in that the deposited substances need to exhibit desired electronic behaviours. A common method to achieve this is to intersperse the ink (a solvent) with nano-particles (small particles with controlled sizes, typically in the order of nano-meters) with desired conductive, dielectric or semiconducting characteristics. The printed substance might be treated post printing in order to evaporate the solvent and/or facilitate a chemical change in the nano-particles. Examples of such treatment include thermal curing [5], curing by ultraviolet light [6], laser sintering [7], e-beam sintering [8], chemical sintering [9] or plasma sintering [10].

Current research efforts are focusing on improving the printing and post-processing technologies available [10-12], improved interconnects [13] and vias [14], improved semiconductors, and printing under less stringent conditions. Examples include printing conductors at room temperature [6] and printing elements such as transistors [15] and diodes [16] with ever increasing performance characteristics. It is forecast that these improvements will continue for some time, as the fastest known inkjet printed transistor has an operating speed of around 20MHz [17-18]. (This is several orders of magnitude behind the capability of existing silicon chip technology.) Researchers are also working on developing transistor characteristics other than maximum frequency. For example, inkjet printing technology has been used to produce flexible and transparent transistors [19].

For those looking to predict where printed electronics will have the greatest future impact, it may pay to think outside the box. In the authour’s opinion, inkjet printing technology is likely to play a larger role in enabling new applications than it is to replace existing electronic technology. It is unlikely that a device with the functionality of a smartphone will be printed anytime soon, but perhaps the capability of printing your own solar panels is closer than you think.

So there has been some substantial change but we aren’t yet at the point where this type of Electronics Design and Manufacture has begun to significantly disrupt the mainstream industry. But I can imagine the day when some of what I do now can be printed and tested right now on my desk instead of having to go through PCB Design, PCB Manufacture and Electronics Prototyping first. Can’t wait for Printed Electronics to become mainstream.

Printed Circuit Board Assembly

Also referred to as a PCA, the Printed Circuit Board Assembly follows on from Printed Circuit Board Manufacture. This is where the components are placed onto the PCB or Printed Circuit Board and the electrical connections formed.

In this post I will focus on volume manufacturing techniques. We also make Printed Circuit Board Assemblies in house by hand loading very small quantities. This is appropriate for prototypes and Niche Manufacturing quantities.

To start with, lets look at the 2 types of components we most work with. The first type is the Through Hole Component. These have pins that go through the PCB to make electrical connection. These components dominated PCB Assemblies until the 1980s when higher PCB loading density requires a change of technology. They are still widely used where mechanical strength, tall components, heavy components or high current levels are involved. An example is shown below with the connectors, relays, transformers and removable components as Through Hole with the Surface Mount Components toward the centre:

Through Hole Technology

The second type is the Surface Mount Component or Surface Mount Device and the overall process is referred to as Surface Mount Technology or SMT. These devices do not require holes through the PCB to mount them and so can be placed closer together and it also improves track routing options because tracks can run on the other side of the PCB without having to avoid the through holes. An example of all Surface Mount assembly is shown below in close up:

Electronics Hardware

Printed Circuit Board Assembly Process

The infographic below was provided by Algen Cruz of Advanced Assembly in the USA. Algen also provided a brief explanation to go with it and I have added that as well. You can click on the infographic to view a larger version.

Printed Circuit Board Assembly

“Design-for-Assembly (DFA), although not as well known as Design-for Manufacturing (DFM), needs to be taken into account during the design phase. And the first step in being able to design-for-assembly is to understand the assembly process. This infographic features this process by showing how a board goes from an unpopulated printed circuit board (PCB) to a final product, ready to be packaged and sent to consumers.” Algan Cruz

PCB Manufacturing Problems

That is a lot of steps. And there are things that can go wrong. The main pitfalls to avoid in the PCB Design Process are:

track widths too narrow

clearances between tracks are too small

acute angle entry to pads

component footprints have pins in the wrong place or the wrong size

component outlines are wrong

silkscreen or overlay over solder pads

via annulus too thin

mounting holes in the wrong place or the wrong size

PCB outline incorrect

PCB 3D profile doesn’t fit into the intended enclosure

And there are a range of issues that can affect the PCB Manufacturing Process. These include:

misalignment of drill holes to tracks to PCB outline routing

internal cut outs missed / not routed

over etching or under etching of the copper

incomplete plated through holes

poor surface finish

poor FR4 and copper bonding or moisture ingress leading to delamination

Maybe you are wondering how a PCB ever gets made successfully? This comes back to undertaking the PCB Design with an understanding of both electronics engineering design principles and the process capability of the manufacturer into account. And when you get it right, the final product can be pretty awesome. A good example can be found at this post about making a Fine Pitch PCB.

PCB Layout

After the Schematic Capture component of the Electronics Design is complete, the logical connections for the electronics components have been determined. If the Electronics CAD package also supports it, you can add rules to guide the Printed Circuit Board Layout, also abbreviated to PCB Layout which we will use from here on.

The PCB provides both the mechanical support for the components and is many cases is a critical part of the circuit since the length of tracks, their thickness, their clearance from other tracks and the relative placement of components and tracks can significantly influence the final performance of the PCB. This is particularly true as power levels, clock speeds or frequency increases.

The Electronic Schematic defines the electrical connections between components, the value of components such as resistors, capacitors and inductors, the type of semiconductors used (silicon chips) and the connectors that take signals and power on and off the PCB. Each item on the schematic has to be linked to a physical shape that will go onto the PCB. This is done by assigning a footprint to the schematic item.

Schematic Symbol

I will explain it works. The Schematic Symbol for an FT232RL USB Serial Interface device is shown below. This is arranged with the signals conveniently placed to suit logical connections and to make the overall Schematic easy to read and understand. The signal name is shown inside the symbol boundary, and the pin number of the IC package is shown on the outside.

FT232RL Schematic Symbol

Schematic Circuit

So this is the symbol for a single part, an IC or Integrated Circuit. The Schematic Circuit or Electronic Schematic shows the connections to the other parts of the circuit. Below we see USB connector wired up the the FT232RL IC and the power supply bypass capacitors. The logic level UART signals are shown at the top right. This section of the Electronic Schematic provides the logical connections for a USB serial interface.

FT232RL USB Schematic

PCB Footprint

Before we can do the PCB Layout, we have to associate the PCB Footprint each Schematic Symbol will use. The PCB Footprint for the FT232RL IC is shown below.

FT232RL PCB Footprint

This is one of the 2 possible footprints for the FT232RL. This one is a 28 pin SSOP package.

Once each Schematic Symbol has a PCB Footprint, we are ready to do the PCB Placement.

PCB Placement

The first step is to create the outline for the PCB and its mounting points, then to place each PCB Footprint so it is in the correct place. For some components, such as connectors, there is a specific place it must go. For other components, there is more freedom to choose the position and there are groups of components that must be in a specific relationship to each other. An example of this are the power supply bypass capacitors which must go very near to the IC they are supporting.

An example of a completed PCB Placement is shown below. This is a USB to RS232 serial converter.

PCB Unrouted

PCB Routing

Now we have the components where we want them, we turn on the autorouter and the PCB is finished. Sorry but I couldn’t help that. The autorouting features of most PCB Layout CAD software packages are never as good as doing it yourself. They can be useful for testing the ease of routing for a particular placement. There are a lot of manufacturing considerations that need to be taken into account and track size requirements, either for current carrying or voltage drop, can be hard to define from just the schematic. And example of this is the main system voltage such as VCC. In some parts of the circuit the required current is low so smaller track sizes are OK, whereas other areas need heavier tracks. It isn’t easy to define this at the schematic level because they are all the same signal or Net.

The PCB with the routing complete is shown below. The selection of track size is related to the current the circuit needs to carry. A good reference for determining the track size is provided by the standard IPC-2222A.

PCB Routed

PCB 3D Cad Integration

It is also important to make sure the PCB will fit into a mechanical enclosure. Most modern PCB CAD tools, such as Altium Designer which we use, can create full 3D models of the PCB. Shown below is an example of just the PCB without the components showing.

Fine Pitch Printed Circuit Board

This example is from a project coming to the end of the Proof of Concept phase. So we have done the Electronics Design and also completed the PCB Layout. I can’t tell you what it does, but you don’t really need to know in order to appreciate the technology. This is an example of a Fine Pitch PCB or Fine Pitch Printed Circuit Board. And even better, it was made right here in Melbourne, Australia.

Pictures first.

RGB Light Emitting Diode Array

Above we have the top surface of a Prototype PCB that drives a 16 x 16 or 256 RGB LED array. The size is 25mm square for the LED Array. You might also have realised that this is a custom RGB LED display. The display is driven as a row x column matrix. This top side has the 16 row drivers.

RGB Light Emitting Diode Array Bottom Side

This is the underside with the 16 x 3 = 48 column drivers.

RGB LED Array Detail

This shows some more detail where the Sea of RGB LEDs is sitting. They are in a staggered offset to reduce jagged edges on the image when it is displayed.

RGB LED Arracy Close Up

This final picture is a close up of the RGB LED array with a lace pin as a size reference. The RGB LEDs are 1mm wide and the pin head is a bit less than 1mm across. This is the smallest pin I could find.

Fine Pitch PCB Technology

Now for some technical details:

4 mil track width (that is 0.1 mm)

4 mil clearance (that is also 0.1 mm)

0.25 mm via hole diameter

The Prototype PCB was manufactured by PCB Fast in Seaford. We use them for our Prototype PCBs because they still manufacture in Australia. And that is part of our focus, maintaining manufacturing in Australia. So I was very impressed with the work they did and thought this was a great way to show what they can do. I was also impressed with the spirit of adventure Kevin and Leeanne had in taking this one on.

That is a lot of links but this is an important part of the process. Get this wrong, and you have a product that doesn’t work.

Electronics Schematic

This the Electronic Circuit Schematic for a 5VDC Switch Mode Power Supply, also known as SMPS. It can deliver up to 0.5A and includes a number of novel features to reduce noise and ripple. The RC damper across D5 is one of these. The other is the 82R series resistor that limits the maximum current through the charge pump diode C14. The measured ripple is less than 1mVRMS.

I’ve gone into a bit of detail because this shows how effective Component Selection can lead to a great outcome. We started with the design objective of a non-isolated power supply to get a 5VDC rail for our circuit from the incoming 12VDC rail. I wanted an efficiency above 80%, low noise, small footprint and low cost. So we looked at a wide range of suppliers including some like Texas Instruments, or TI as they are usually referred to, who have tools on their websites that will select suitable components for you. In this case they didn’t have a suitable offering but Microchip did.

And the Schematic above is the result of the Component Selection process, review of the datasheet to get the circuit requirements for things like calculating the output voltage feedback divider (R10 and R12) correctly. And now we have our Schematic ready for creating the PCB Layout.

Electronics Design

The Electronics Design Process involves a number of steps. Unless what you are doing is a minor tweak to an existing product, you will use these steps. Over the next few weeks I will unpack what is involved in each step but this post is just going to be the list of steps.

The overall process for Product Development for an Electronics Products follow like this:

Successful Endeavours Development Process

And there are many options for the technology to use, all of which have their merits and drawbacks.

Design For Manufacture

Electronics products almost invariably have a Printed Circuit Board , PCB, on the inside. This is one of the most common things we do, designing the Printed Circuit Board on the inside on the product. Now designing a Printed Circuit Board so it works correctly is one thing, but if you are going to make them cost effectively in volume then you have to consider the manufacturing options at your disposal. To achieve Low Cost Electronics Manufacture requires every aspect of the design to be considered. The following video covers the basic issues very well:

So the things to focus on are:

Use SMT as much as possible,

Reduce the number of components by using more highly integrated circuits,

Reduce the variety of components so the number of reels is reduced,

Ask the PCB loader about their standard panel sizes. If you can adjust the PCB size to suit them then it will reduce their costs,